Dislocation engineering using a scanned laser

ABSTRACT

A method for generating patterned strained regions in a semiconductor device is provided. The method includes directing a light-emitting beam locally onto a surface portion of a semiconductor body; and manipulating a plurality of dislocations located proximate to the surface portion of the semiconductor body utilizing the light-emitting beam, the light-emitting beam being characterized as having a scan speed, so as to produce the patterned strained regions.

BACKGROUND

This invention relates to a system and method for manipulatingdislocations in semiconductor devices using a scanned laser.

Currently, 65 nanometer (nm) technology and beyond makes extensive useof strain engineering to optimize device performance. The appearance anduncontrolled behavior of dislocations in this context is a frequentsource of problems, since these defects provide electrical leakage pathsand also lead to undesired local strain variations. At the same time,the deliberate relaxation of strained layers by dislocation motion is acommon technique of preparing substrates on which strained layers can begrown.

An economic determinant of integrated circuit process technology is theyield, that is, the percentage of the total number of chips processedthat are good. The yield of complex integrated circuits is typically afew percent. One major factor that affects this yield is the presence ofcrystal defects in silicon, or in other semiconductor wafers on whichintegrated circuits are built. Some of these crystal defects can beclassified as dislocations, which can be introduced in high temperatureprocessing when large strains are present.

SUMMARY

An exemplary embodiment of a method for generating patterned strainedregions in a semiconductor device includes directing a light-emittingbeam locally onto a surface portion of a semiconductor body; andmanipulating a plurality of dislocations located proximate to thesurface portion of the semiconductor body utilizing the light-emittingbeam, the light-emitting beam being characterized as having a scanspeed, so as to produce the patterned strained regions.

An exemplary embodiment of a method for generating patterned strainedregions in a semiconductor device includes directing a laser beamlocally onto a surface portion of a semiconductor body; operating thelaser beam in a first mode of operation or a second mode of operation,the laser beam being characterized as having a scan speed; andmanipulating a plurality of dislocations located proximate to thesurface portion of the semiconductor body utilizing the laser beam so asto produce the patterned strained regions, the plurality of dislocationsbeing manipulated during the first mode of operation and the second modeof operation.

An exemplary embodiment of a system for manipulating dislocations onsemiconductor devices includes a semiconductor body having a pluralityof dislocations; and a moveable laser configured to generate a laserbeam locally on a surface portion of the semiconductor body, themoveable laser being characterized as having a scan speed, the moveablelaser manipulates the plurality of dislocations proximate to the surfaceportion of the semiconductor body by adjusting the temperature and thescan speed of the laser beam.

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other objects, features, andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are various schematic cross sectional views of an exemplarysemiconductor device subjected to a blow-down technique for manipulatingsubstrate dislocations, in accordance with one exemplary embodiment ofthe present invention;

FIG. 4 illustrates an exemplary microphotograph of a portion of across-sectional side view of a wafer exhibiting the blow-down phenomenain accordance with one exemplary embodiment of the present invention;

FIGS. 5A and 5B are cross sectional views of an exemplary semiconductordevice subjected to a surfing technique for manipulating substratedislocations, in accordance with another exemplary embodiment of thepresent invention;

FIG. 6 is a cross-sectional view of an exemplary semiconductor devicesubjected to the surfing technique for manipulating substratedislocations to allow the generation of uniaxial strained regions, inaccordance with one exemplary embodiment of the present invention; and

FIG. 7 is a cross-sectional view of an exemplary semiconductor devicesubjected to the surfing technique to remove threading dislocations froma relaxed strained layer, in accordance with one exemplary embodiment ofthe present invention.

The detailed description explains the preferred embodiments of theinvention, together with advantages and features, by way of example withreference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

The present invention and the various features and advantageous detailsthereof are explained more fully with reference to the non-limitingembodiments that are illustrated in the accompanying drawings anddetailed in the following description. It should be noted that thefeatures illustrated in the drawings are not necessarily drawn to scale.Descriptions of well-known or conventional components and processingtechniques are omitted so as to not unnecessarily obscure the presentinvention in detail. The examples used herein are intended merely tofacilitate an understanding of ways in which the invention may bepracticed and to further enable those of skill in the art to practicethe invention. Accordingly, the examples should not be construed aslimiting the scope of the invention.

Exemplary embodiments of the present invention provide systems andmethods for manipulating dislocations in various semiconductortechnologies by a light-emitting beam (e.g., laser beam). Dislocationssubject to the beam will move where the beam is incident, allowing bothtemporal and spatial control of dislocation evolution. Such systems andmethods provide modes of operation that illustrate two phenomenareferred to herein as the blow-down and surfing phenomena. Thesephenomena can be utilized to perform various dislocation manipulations.

The inventors herein have recognized that the systems and methodsdescribed herein eliminate dislocations present in silicon on insulator(SOI) technology devices. The systems and methods described hereinfurther control dislocation growth during high-temperature laserannealing (LSA) and enable localized (patterned) relaxation of layerstrain. The systems and methods described herein further enable thegeneration of uniaxially strained regions and enable the elimination ofthreading dislocations in a relaxed strained layer. Such systems andmethods further enable the generation of specific dislocation patternsand their associated strain fields for use as templates for thespatially controlled grow of epitaxial islands and nanostructures.

For a better understanding of the invention and its operation, turningnow to the drawings, FIG. 1 illustrates a portion of a semiconductorbody or wafer, designated generally by 10. In accordance with oneexemplary embodiment, the wafer is made up of silicon. Of course, othersuitable materials can be used to form the wafer such as germanium,gallium phosphate, gallium arsenide or the like. The wafer 10 sits on aninsulating layer, for example a buried oxide surface layer, which isindicated as lying below the dashed line 12. The semiconductor body 10is fabricated to include active regions 14 where current flows and wheresemiconductor devices, such as transistors integrated circuits or thelike, are to be formed. The wafer configuration can be varied to achievevarious goals and should not be limited to the configurations shownherein. In other words, the configurations described herein are intendedto illustrate the methods for manipulating dislocations on semiconductortechnology and semiconductor substrates, thereby should not limit thescope of the exemplary embodiments of the present invention.

In accordance with one exemplary embodiment, a moving light-emittingbeam, which is indicated by arrow 16, directly scans over a surfaceportion of the wafer 10, and particularly over the active regions 14configured on the wafer 10. More specifically, the light-emitting beam16 heats the wafer 10 locally allowing dislocations present on the wafer10 and most importantly on the active regions 14 to move by increasingtheir mobility. Dislocations move due to pre-existing strains (e.g.,SiGe on Si wafers) and because the beam producing source (e.g., laser)itself generates a large stress field moving along with the beam. As thedislocations are driven into the buried-oxide layer and theshallow-trench oxide, this effectively eliminates undesirable electricalleakage paths from forming.

The light-emitting beam can be generated through any source-type, suchas a laser, configured to vary the temperature, the sweep speed, theabsorption profile, and the spot-size of the beam. However, other beamsfrom other sources may be used such as, for example, a lamp. Forsimplistic purposes, the methods herein will be described in the contextof using a laser beam from a scanned laser device. Such a device is usedin a scanned laser-annealing (LSA) configuration to move thedislocations as described herein. However, other configurations can beused in other exemplary embodiments of the present invention and shouldnot be limited to the examples set forth herein.

In accordance with one exemplary embodiment, the laser beam 16 iscontrolled such that two distinct modes of operation for manipulatingdislocations can be implemented. The first mode of operation is referredto herein as a “blow-down”. In this mode of operation, stress from thelaser beam 16 drives dislocations into the substrate or into absorbingsinks such as buried oxide (BOX) layers 18 or into shallow trenchisolation (STI) structures 19 as shown in FIG. 1. This mode of operationenables the elimination of already present dislocations in the wafer 10.

A better illustration of how the blow-down technique manipulatesdislocations on semiconductor devices is shown in FIG. 2. A pre-existingdislocation or dislocation loop, generally designated by 20, below awafer surface 22 is subjected to a laser beam 24 having a scan directionindicated by arrows 26. The laser beam 24 locally heats the region belowthe wafer surface 22. As a result, the dislocation 20 grows or increasesin size while in the hot spot of the laser beam 24 as shown. Thedislocation 20 moves where the beam is incident. The dislocation motionis indicated by arrows 28. The blow-down phenomenon occurs by itselfwhen the maximum velocity reached by the dislocation 20 is less than thescan speed of the laser beam 24 as illustrated in FIG. 2. Thedislocation 20 grows to the micron scale, but stops growing once thelaser beam 24 passes the dislocation 20 as illustrated in FIGS. 3A and3B. FIG. 3A illustrates the dislocation 20 before the laser beam 24passes through it while FIG. 3B illustrates the dislocation 20 after thelaser beam 24 passes through it. Although the blow-down effect isdescribed using an LSA configuration, the blow-down effect may alsooccur using a flash annealing configuration.

FIG. 4 illustrates a portion of a cross-sectional side view of wafer 10in a magnified form. This exemplary figure shows the blow-down phenomenaobtained by direct transmission electron microscopy (TEM) observations.Of course, other tools and methods of viewing the blow-down phenomenacan be used as desired. This exemplary figure shows dislocations 20blown down and away from the active region 14 by a 1250-Centigrade (C)laser scan.

FIG. 5A-5B illustrates a second mode of operation in accordance with oneexemplary embodiment. The second mode of operation is referred to hereinas “surfing”. Using the previous example to describe this mode ofoperation, surfing occurs when the temperature of the local hot spot ofthe laser beam 24 is placed high enough and the combination of laserstress and pre-existing layer strains is large enough to allow thedislocation 20 to grow with a speed that matches the speed of the laserbeam 24. In other words, surfing occurs when the maximum value reachedby the dislocation velocity equals or exceeds the scan speed of thelaser beam. In this mode of operation, the laser beam 24 is controlledsuch that one end of the dislocation 20 keeps up with the moving hotspot of the laser beam 24, resulting in dislocation growth over thelength of the laser scan. FIG. 5A illustrates the dislocation before thehot spot of the laser beam passes through the dislocation while FIG. 5Billustrates the dislocation after the hot spot of the laser beam passesthe dislocation. As shown, one end of the dislocation 20 moves with andin the scan direction 26 of the laser beam 24. Surfing occurs only in anLSA configuration in accordance with one embodiment.

In accordance with one exemplary embodiment, surfing can be used togenerate desired dislocation patterns or relax specific regions of astrained-engineering pattern by moving dislocations from a dislocationsource into other areas. In other words, the laser beam can be used todraw out dislocations from any point on a layer along various paths asdesired in an “etch-a-sketch” fashion.

In accordance with one exemplary embodiment, the temperature and dwelltime (laser spot thickness/LSA scan speed) of the laser beam play a rolein manipulating dislocations of various sizes in semiconductortechnology. Dislocations become more active at higher temperatures anddepending on the desired mode of operation the scan speed of the laserbeam will determine whether dislocations will grow over the length ofthe scan. In accordance with one exemplary embodiment, surfing-typegrowth generally occurs when the temperature of the laser beam isapproximately above 1250 C and the scan speed is greater than about 1millisecond (ms). At significantly lower temperatures or lower dwelltimes, surfing should not occur. For example, surfing does not occur ona 40 nano-micron (nm) dislocation loop when scanning a laser beam with a1498 Kelvin (K) scan, while surfing occurs with a 1624 K scan. Thus, thetemperature and scan speed can be adjusted to avoid draggingdislocations from one part of the wafer to another. It should beunderstood that different wafer materials may affect the temperaturesand dwell times needed to move dislocations from semiconductortechnology or into the same depending on the application.

The direction of the laser scan can also play a role in separatelymanipulating dislocations of various kinds in semiconductor technologyin accordance with one exemplary embodiment. Dislocations move only onspecific glide planes. Thus, dislocations on glide planes orientedperpendicular to the scan direction of the laser beam will not exhibitthe surfing phenomena. Only dislocations on glide planes oriented alongthe scan direction are subject to the surfing phenomenon. Thus, thelaser beam can be controlled so that only dislocations on glide planesoriented in one direction can be manipulated to obtain a desireddislocation pattern or a desired degree of asymmetric relaxation.However, all dislocations will exhibit the blow-up phenomena in somedegree when the laser passes the dislocations.

Dislocations on the wafer 10 can also be manipulated by adding astrained layer to the wafer 10 in accordance with one exemplaryembodiment. Since dislocations move in response to strain(thermal-mismatch), adding additional strain to existing dislocations onthe wafer 10 will enable the dislocations to move more quickly. Forexample, surfing may occur when adding a 50 nm, 1% strained layer on awafer subjected to a 1498 K laser scan.

Using different strain-inducing materials can also be used to manipulatedislocations since dislocations respond differently with differentstrain-inducing materials. In other words, dislocations move better withsome materials and not with others. For example, surfing may not occuron dislocations in the 1498K scan with the strained layer as describedabove when the mobility of the dislocations is reduced by, for example,a factor of three.

In accordance with one exemplary embodiment of the present invention,the methods described herein can be used to manipulate dislocations suchthat uniaxial layer relaxation or strain generation is provided. FIG. 6illustrates how to provide uniaxial layer relaxation or straingeneration. In this exemplary figure, the wafer 10 is fabricated toinclude an implanted region 50 and a non-implanted region 52. Inaccordance with one embodiment, a raster scan generator raster scansfrom the implanted region containing dislocations into the non-implantedregion, filling the latter with oriented dislocations. In operation, theimplanted region is subjected to the laser beam 16 such that strain inthe non-implanted region 52 is relaxed in one direction, thereby leavingstrain only in one direction. Such a configuration can be useful forvarious applications.

In accordance with one exemplary embodiment, the surfing technique canbe used to also remove threading dislocations from a relaxed strainedlayer as illustrated in FIG. 7. Here, any threading dislocations (i.e.ones that extend to the surface) can be swept out of the region ofinterest by rastering a laser beam operating in the surfing mode. Thisremoves potential sources of leakage paths from the region of the waferon which microelectronic devices are to be constructed.

In the above embodiment, varying the temperature, the sweep speed, theabsorption profile, and the spot-size of the laser beam 24 effectivelyvaries the dislocation evolution. Various modeling techniques can beused to predict the phenomena described above and can be validatedthrough direct experimental observations.

While the preferred embodiment to the invention has been described, itwill be understood that those skilled in the art, both now and in thefuture, may make various improvements and enhancements which fall withinthe scope of the claims which follow. These claims should be construedto maintain the proper protection for the invention first described.

What is claimed is:
 1. A method for removing dislocations from asemiconductor device, comprising: directing a light-emitting beamlocally onto a surface portion of a semiconductor body that includesactive regions of the semiconductor device; and manipulating a pluralityof dislocations located proximate to the surface portion of thesemiconductor body utilizing the light-emitting beam, the light-emittingbeam being characterized as having a scan speed; wherein manipulatingthe plurality of dislocations comprises directly scanning the pluralityof dislocations with the light-emitting beam to drive the plurality ofdislocations away from the surface portion of the semiconductor body andinto a buried oxide layer, the buried oxide layer is disposed as acontinuous and uninterrupted layer below the semiconductor bodyincluding the active regions and below silicon trench isolation regionsdisposed adjacent to the active regions, and the scanning enabling theelimination of the plurality of dislocations from the surface portion ofthe semiconductor body.
 2. The method as in claim 1, wherein thelight-emitting beam operably controls the motion of the plurality ofdislocations during scanning.
 3. The method as in claim 1 wherein thelight-emitting beam drives the plurality of dislocations away from thesurface portion of the semiconductor body when the plurality ofdislocations move at a maximum velocity less than the scan speed of thelight-emitting beam.
 4. The method as in claim 1, wherein at least oneend of each of the plurality of dislocations moves simultaneously withand in the scan direction of the light-emitting beam when thelight-emitting beam scans across the plurality of dislocations.
 5. Themethod as in claim 1, wherein the plurality of dislocations ismanipulated utilizing the light-emitting beam to generate specificdislocation patterns on the semiconductor body.
 6. A method for removingdislocations from a semiconductor device, comprising: directing a laserbeam locally onto a surface portion of a semiconductor body thatincludes active regions of the semiconductor device; operating the laserbeam in a first mode of operation, the laser beam being characterized ashaving a scan speed; and manipulating a plurality of dislocationslocated proximate to the surface portion of the semiconductor bodyutilizing the laser beam; wherein the first mode of operation comprisesdirectly scanning the plurality of dislocations with the laser beam todrive the plurality of dislocations away from the surface portion of thesemiconductor body and into a buried oxide layer, the buried oxide layeris disposed as a continuous and uninterrupted layer below thesemiconductor body including the active regions and below silicon trenchisolation regions disposed adjacent to the active regions and thescanning enabling the elimination of the plurality of dislocations fromthe surface portion of the semiconductor body.
 7. The method as in claim6, wherein the laser beam operably controls the motion of the pluralityof dislocations during scanning.
 8. The method as in claim 6, whereinthe laser beam drives the plurality of dislocations away from thesurface portion of the semiconductor body when the plurality ofdislocations move at a maximum velocity less than the scan speed of thelaser beam.
 9. The method as in claim 6, wherein at least one end ofeach of the plurality of dislocations moves simultaneously with and inthe scan direction of the laser beam when the laser beam scans acrossthe plurality of dislocations.
 10. A system for manipulatingdislocations on semiconductor devices, comprising: a semiconductor bodyincluding active regions having a plurality of dislocations thesemiconductor body disposed on a continuous and uninterrupted buriedoxide layer arranged below the semiconductor body including the activeregions and below silicon trench isolation regions disposed adjacent tothe active regions; and a moveable laser configured to generate a laserbeam locally on a surface portion of the semiconductor body, themoveable laser being characterized as having a scan speed, the moveablelaser manipulates the plurality of dislocations on the surface portionof the semiconductor body by adjusting the temperature and the scanspeed of the laser beam to drive the plurality of dislocations from thesemiconductor body into the buried oxide layer.